This invention relates to a hermetic high side rotary compressor and, more particularly, to a valve for blocking the discharge flow in said type of compressor which is commonly used in small refrigerating machines.
A high side rotary compressor has as an operating characteristic that each time the compressor stops there is migration of refrigerant gas fluid from the pressurized housing to the evaporator through the condenser and capillary tube of the refrigerating system. Said migration of hot fluid to the evaporator each time the compressor periodically stops causes loss in the refrigerating capacity of the system (about 12%). Thus, in addition to heating the evaporator with a hot fluid mixture, the compressor has to re-establish the normal operating cycle each time it starts, that is, re-establish the regular operation pressure and temperature levels in each unit of the refrigerating system including the compressor itself.
A normally known solution to block the discharge fluid migration from the compressor housing to the condenser of the refrigerating system is to use a piston type flow blocking valve which is connected to the suction line by a capillary and acts in the following manner. When operating, the pressure suction line acts through the capillary upon a piston having a hole on the corner, being mounted to the discharge tube and leaves the passageway open for the gas through the hole discharge. When the compressor stops, the suction pressure stops acting and a spring returns the piston to the closed position, thereby avoiding the high pressure gas flow to be supplied into the refrigerating system.
A serious drawback to the known solution is that it is difficult to seal the cooling fluid leakage in the high pressure side acting on the piston of the valve up to the suction tube through the capillary tube of the valve. Said leakages cause losses in the compressor volumetric capacity since they are directly toward the suction. Attempts to minimize leakages in said type of blocking valve have as a result complex constructions and high cost.